1. Field of the Invention
The invention relates generally to a medical instrument for use in endoscopic surgical procedures, and more particularly to an endoscopic surgical instrument capable of rotatably manipulating an attached surgical tool.
The burgeoning field of endoscopic surgery utilizes surgical instruments with slender barrel portions for entering cannulas placed in small incisions or wounds in the patient's body. The advantages of Endoscopic surgery over conventional open procedure surgery are due in large part to elimination of the need to make large incisions in the patient, and include reduced patient trauma, quicker recovery time and a significantly lower chance of infection.
The distal end of the barrel portion of an endoscopic instrument can be provided with a precision surgical tool, such as a pair of jaws or a pair of scissors, for performing various surgical tasks such as gripping tissue or body organs, cutting ligaments, and the like. The surgical tool is actuated by a handle assembly attached to a proximal end of the barrel portion and operated by a surgeon/user.
With the working length of the endoscopic surgical instrument, i.e., the portion of the instrument inserted into the cannula, typically being 12 inches or more, it is desirable to provide the surgeon/user with means to precisely maneuver the surgical tool at the distal end after the instrument is inserted into the patient's body. Moreover, when an endoscopic surgical instrument is inserted into an insufflated body cavity, it is desirable to create an airtight seal between the cannula and the barrel portion. To preserve this seal, relative movement between the barrel portion and the cannula should be kept to a minimum.
2. Description of the Prior Art
A conventional endoscopic surgical instrument typically includes a handle assembly and a slender, elongated barrel portion attached at its proximal end to the handle portion. A distal end of the barrel portion has a surgical tool, or attachment, such as a pair of gripping jaws for gripping tissue or other internal body parts. The slender barrel portion is inserted through the cannula in the patient's body and the handle portion is operated by the surgeon/user to mechanically operate the surgical tool.
Endoscopic surgical instruments have advanced mechanically to the point where they are capable of orienting the surgical tool, that is, angularly rotating the tool about the longitudinal axis of the surgical instrument, to properly align the surgical tool while allowing the surgeon/user to operate the handle assembly in a normal, comfortable position. For example, U.S. Pat. No. 4,258,716 is directed to an endoscopic instrument that includes a pair of rotary cutting scissors at the distal end of a shaft assembly. A first set screw is used to lock a pair of scissor blades in position relative to each other, i.e, regulate the blade opening, and a second set screw locks the set of blades in a set angular position with respect to the longitudinal direction of the shaft assembly. However, the set screws must be tightened and the adjustments made before the endoscopic instrument is inserted through the cannula.
An improved endoscopic surgical instrument is disclosed in European Patent Application No. 543,107, published May 26, 1993. The instrument features a handle assembly with a knob that can be rotated by the surgeon/user to rotate the entire elongated body assembly and orient a surgical attachment at various angles with respect to the longitudinal axis of the instrument. International Publication No. WO 93/01754, published Feb. 4, 1993, discloses an endoscopic surgical instrument that includes a plug for rotating an outer tube 12 and orienting a clamp-like tip assembly at any desired angle relative to the longitudinal axis of the instrument. However, with these surgical instruments there is a drag force created by relative movement between the rotated outer tube and the cannula. The drag force makes it difficult to rotate the outer tube, and can also compromise the seal between the outer tube and the cannula, leading to pneumoperitoneal loss in the insufflated body cavity.
Accordingly, further improvements in endoscopic surgical instruments capable of angularly orienting a surgical tool are needed. Other desirable improvements include provision of a surgical instrument designed for easy cleaning and sterilization after each use and of a surgical instrument with better overall mechanical performance.